How mobile networks work

Mobile phones work by converting voice, text, multi-media messages or data calls into radio waves or Radio Frequencies. RF radiation is a subset of electromagnetic radiation with a wavelength of 100km to 1mm, which is a frequency of 300 Hz to 3000 GHz, respectively.


SIM
GSM mobile phones require a small microchip, called a Subscriber Identity Module or SIM Card, to function.  SIM Card is usually placed underneath the battery in the rear of the unit, and (when properly activated) stores the phone's configuration data, and information about the phone itself, such as which calling plan the subscriber is using. When the subscriber removes the SIM Card, it can be re-inserted into another phone that is configured to accept the SIM card  and used as normal.

GSM-Global System for Mobile communications

1. SIM Card carries the user's identity for accessing the network and receiving calls.
2. All calls are charged against their SIM card account.
3. It is also equipped with a memory to store telephone numbers along with names.
4. It also enables you to send and receive short messages ( SMS).

Mobile phones connect to the base station providing the best signal - usually the nearest. As a person moves away from the base station the signal becomes weaker, so the mobile phone automatically adjusts its own RF field strength to maintain the minimum level needed to communicate with the base station.